I'd recommend getting engine set up for one pipe and leaving it that way, if you plan to re-jet the carb every time you change pipes and such I guess that will be OK, but I can tell you that you will get better all around performance with the YZ pipe from low end all the way up to top end, I personally wouldn't bother with that tiny little pipe if I had a nice YZ pipe set up.
I have a couple of the pocket bike pipes myself and they do ok for a moderate build, but remember that any time yoy can flow more air through that engine you will need to make sure you are putting more fuel in the mix also, if not you'll likely end up with a lean run condition and could cook your engine.